1. Field of the Invention
This invention relates to an analytic technology for bromine-type flame retardants, particularly volatile detrimental compounds contained in the flame retardants, by spectrophotometry such as infrared spectrophotometry and Raman spectrophotometry. More particularly, the present invention relates to a method and an apparatus each used for analyzing, with high accuracy and high sensitivity, those residual organic contaminants which are contained in bromine type flame retardants blended into plastic materials or rubber materials and, among others, polybromobiphenyl (PBB), a polybromodiphenylether (PBDE) such as decabromodiphenylether (DBDE), and other volatile bromine compounds, by using an economical apparatus and a simple analytic technology. The analyzing method and the analyzing apparatus according to the invention are particularly useful for analyzing bromine compounds of bromine-type flame retardants used in plastic members of electronic appliances and home electrical appliances.
2. Description of the Related Art
When members exposed to a high temperature or to a high voltage are formed of plastic materials or synthetic rubber materials in, for example, electronic appliances, home electric appliances and medical equipment, flame retardants have often been blended in these materials. Though various types of flame retardants are known, bromine-type flame retardants such as PBB, PBDE, etc, have drawn increased attention in recent years. This is because these flame retardants not only generate toxic substances (for example, brominated dioxines) equivalent to dioxine when they are burnt at 300 to 600° C. but they may also operate as environmental hormones (hormone disturbing substances).
In view of such serious problems, efforts to the restrict the use of bromine-type flame retardants has proceeded in major countries. A typical example is observed in the EU, that is, “RoHS Directive (Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment)” enforced on Jul. 1, 2006. This restriction inhibits the use of PBB, PBDE, etc, in electronic and electrical equipment. As a matter of fact, detrimental substances such as PBB and PBDE contained in these products must have a concentration of 1,000 ppm or below. Manufacturers of these products must correctly analyze before the production of the products whether or not plastic materials and the rubber materials contain detrimental substances such as PBB and PBDE.
Technologies for analyzing and detecting flame retardants, and the elements constituting them, in the plastic materials used for producing the electronic appliances and the home electric appliances have been known in the past. For example, Japanese Unexamined Patent Publication (Kokai) No. 2000-292350 describes an identification apparatus for resins, including a small chamber having an open portion at one of the ends thereof, means for thermally decomposing a resin specimen kept in contact with the open portion, means for introducing a decomposition gas generated by the resin specimen into the small chamber and conveying it to infrared spectrophotometry means, and means for comparing and collating the spectrum obtained by the infrared spectrophotometry means with the spectrum of a resin that was generated in advance. By the way, this patent document does not describe the detection of detrimental substances such as PBB and PBDE.
Japanese Unexamined Patent Publication (Kokai) No. 2000-241321 describes a spetrophotometric system, using a thermal decomposition infrared spectrophotometry, which irradiates a laser beam onto a material as an object of spectrophotometry, thermally decomposes the material and acquires infrared absorption spectra from the thermal decomposition gas. Incidentally, this patent document also does not describe the detection of detrimental substances such as PBB and PBDE.
Japanese Unexamined Patent Publication (Kokai) No. 2005-283336 describes the detection of detrimental substances such as PBB and PBDE. This patent document describes an additional substance content judgment program for judging whether or not a predetermined substance (PBDE or PBB) is contained in a measurement object, formed of an unknown plastic material as a base, by utilizing the spectra acquired by subjecting the measurement object to Fourier transform infrared spectrophotometry (FTIR). However, this patent document only teaches use of an unknown plastic as the measurement object.
As can be understood from the facts described above, the prior art technologies for analyzing and detecting the flame retardants in the plastic materials and the elements constituting the flame retardants need complicated constructions for the analyzing apparatus or the analyzing system and an analyzing operation is also extremely complicated. The analysis has a low sensitivity when an economical apparatus and a simple analyzing technology are used. When an expensive apparatus is used, on the contrary, high-sensitivity analysis becomes possible but an expert in analytical technology becomes necessary.
An explanation will be given more concretely. The economical apparatus is an infrared spectrophotometer or a Raman spectrophotometer and can be bought for ¥10,000,000 or less. However, these spectrophotometers can detect the measurement object compounds. such as PBDE and PBB. only when they are contained in an amount of at least 1% by weight in the plastic material, and high sensitivity analysis cannot be expected. Determination is not possible when the infrared peak peculiar to the plastic material and the peak peculiar to the measurement object compound are closed to each other.
On the other hand, a gas chromatography mass spectrograph corresponds to an expensive apparatus and costs as much as ¥20,000,000 or more. When the analysis is conducted by using this mass spectrograph, too, pre-treatment (solvent extraction) is essentially necessary for preparing a measurement sample and the analytic operation is complicated. Further, this mass spectrograph includes the case where a suitable solvent does not exist for the solvent extraction. In such a case, the measurement object compound cannot be detected though the measurement apparatus has a high sensitivity because the compound exists in only an extremely small amount.